The World’s Greatest Fault Passage Indicators

Ensto Protrol makes the best product in the world for secondary substation automation. Ensto will help them go global.

In the early 2000s, there was much discussion in utility companies all over Sweden, and a hard look was given to how secondary substations might look in the future, with special concentration on what kind of equipment would be necessary to gain a more flexible electricity distribution network. An industry work group defined the specs, and engineers went to work.

Two of those engineers were Bo Almér and Torbjörn Karlsson, who had recently created a company called Protrol, a portmanteau combining “protection” and “control.” (Sorry, fans of northern legends, the name has nothing to do with trolls.)

Enter Gudrun

Then Gudrun came along and gave underground cable its push. The cyclone that hit Scandinavia in January of 2005, with winds gusting up to 165 kilometers per hour, was equal to a Category One hurricane. In Sweden alone, Gudrun destroyed 75 million cubic meters of forest and caused 415,000 homes to lose power, some for several weeks. It was one of the biggest environmental disasters in Swedish history, and it caused rural areas in Sweden to lay cable underground with a new sense of urgency.

“The real challenge with putting utility lines underground is finding the fault,” says Karlsson, Managing Director of Ensto Protrol. “With overhead lines you knew from experience that it’s probably the trees on the hill that need cutting back again.” But underground was anybody’s guess. “The line might be 20 kilometers long. Where’s the fault? It could take 12 to 24 hours to find it by testing.”

Smart tech for underground

So the Protrol engineers created smart technology to identify and isolate the faulty section and feed power back to customers within minutes. “Our novel idea was to measure three-phase currents to detect the earth fault current,” says Karlsson. “The real benefit is that you don’t need to measure voltage, and that makes the secondary substation much more cost effective.” Protrol patented their technology in Sweden and Europe.

Protrol's fault passage indicators (FPIs), its IPC402x devices, are of two types. The more basic application communicates with a control center, which takes the next step to isolate the faulty section. In the more advanced application, detectors communicate with their closest neighbor to take immediate action, isolating the fault and minimizing the outage time. Protrol's FPI technology includes overcurrent, Protrol's earth fault, non-directional earth fault and phase break detection functions. This technology is applicable not only in underground cable, but for overhead lines, as well.

If this tech talk has lost you, then take it from Ensto's Harri Tuononen, Ensto Finland’s Sales Manager, Network Automation: "It's the only fault indicator of its kind I've seen that works flawlessly. It's everything you need outside the primary substation."

A family company, not a holding company

Of course, a lot of companies were interested in buying Protrol. “We were contacted by many potential buyers,” says Karlsson, “but they were usually venture capitalists who wanted to buy companies because they understood that the electricity business is good business. But we’d built the company, and we wanted to see that there was potential for growth.”

When Ensto came along in 2021 things made sense: Ensto was a family company, not a holding company. And Protrol fit into Ensto’s vision to become a leading expert for DSOs. “With Ensto there really is no overlap in our businesses. We offer a smart technology that makes sense for their business, and they’re able to offer us access to the rest of the world.” In December 2021, Ensto concluded the purchase of 70 percent of Protrol.


Ensto Protrol is based in Mölndal, Sweden, outside Gothenburg, and has 10 employees. It’s the market leader in Sweden, and now their products have been well received in other Ensto markets, especially in Asia. The key to success, says Karlsson, is to stay ahead of the competition and protect your IP.

Karlsson says our greatest challenge right now is preparing to export. “You’ve got to understand the requirements of each market. There are no standard solutions, and you can even have different specs within a single country.” And as it expands, Ensto Protrol must stay focused on its business in Sweden where it’s the market leader in the automation of secondary substations.

But all of these are problems of the “good” variety, the very reason it partnered with Ensto, a company that could share the burden and accelerate taking Protrol products to the world.


Read more about the fault passage indicators